This invention relates to a conveyor for feeding portions of sheet material to a user machine.
In particular, the present invention relates to an inlet or loading station for a continuous belt conveyor for feeding preshaped or punched pieces of cardboard or the like to a machine for packaging cigarettes into hinged lid packets from an accumulation and feed apparatus for said preshaped or punched pieces.
Italian patent No. 992.092 corresponding to U.S. Pat. No. 3,953,021 of the same applicant relates to an accumulation and feed apparatus of the aforesaid type in which the preshaped pieces to be fed to said packaging machines are continuously fed into a column vessel or magazine down which they descend by gravity, and from the lower end of which they are individually withdrawn by pneumatic extractor means and deposited on an inlet conveyor of a packaging machine.
Italian patent application No. 3421-A/76, filed May 6, 1976, corresponding to copending U.S. Application Ser. No. 791,327, filed Apr. 27, 1977 of the same applicant describes a conveyor comprising a flat support and slide surface for said preshaped pieces, along which these latter are fed stepwise by transverse mobile elements forming conveying compartments which exactly define the longitudinal position of the preshaped pieces along the conveyor.
The position of the preshaped pieces in a direction transverse to their feed direction is defined by shoulders carried by said flat support and slide surface and arranged to cooperate with the transverse opposing ends of the preshaped pieces. Finally, each preshaped piece is kept inside the relative conveying compartment by a vertical guide comprising at least one vertical knife disposed above said support and slide surface and defining therewith a slot in which the preshaped pieces slide. The use of such a vertical guide is made necessary by the very high frequency (up to seven steps per second or more) with which said conveyor is made to advance, and which otherwise would result in the immediate escape of the preshaped pieces from their conveying compartments.
The need to use a vertical guide requires the solution to a technical problem relative to loading the preshaped pieces on to the conveyor. This loading is in fact done from above at a conveyor inlet station by pneumatic extractor means, in particular suckers, which move with reciprocating motion to and from said support and slide surface in order to withdraw the preshaped pieces one by one from the bottom of said column vessel and deposit them on said support and slide surface below said vessel.
The presence of a vertical guide at said inlet station would hinder the aforesaid top loading, whereas on the other hand the absence of a vertical guide for the preshaped pieces at said inlet station would be inadmissible as it is precisely at this station that the vertical instability of the preshaped pieces is greatest.